Overview
ISO 18487-1:2017 - "Aerospace series - Titanium tube for 35 MPa operating pressure - Part 1: Inch series" - is an international standard that defines technical requirements for seamless titanium alloy tubing used primarily in aerospace systems rated for 35 MPa (5 080 psi, Pressure Class J). The document harmonizes dimensions, materials, manufacturing and test requirements for inch-series tube sizes commonly used in hydraulic and fluid systems in aircraft and space vehicles.
Key topics and technical requirements
- Scope and applicability: Seamless circular titanium tubing intended for systems with 35 MPa operating pressure, but not restricted to those applications.
- Dimensions and tolerances: Nominal inch-series sizes are specified with SI units; dimensional requirements reference ISO 8575 and tolerances reference ISO 12573.
- Chemical composition: Composition limits are defined for alloying elements and impurities. Example ranges include Al 2.50–3.50%, V 2.00–3.00%, with strict limits on interstitials (O ≤ 0.120%, N ≤ 0.020%, H ≤ 0.005%). Analytical methods (ASTM/EN) are referenced.
- Melting practice: Multiple melts with inert gas flooding are required; open-air furnace melting is not permitted. Vacuum arc remelting (VAR) is required for second and subsequent melts.
- Heat treatment and delivery condition: Cold-worked, stress-relieved in vacuum or inert atmosphere at a minimum of 370 °C for 30 minutes; rotary straightening after final heat treatment is not permitted.
- Mechanical properties: Tensile testing at 15 °C with specified tensile strength, 0.2% proof stress and elongation criteria (see Table 2 in the standard). Sample size and reporting requirements are specified.
- Microstructure and CSR: Microstructure inspection (≥400×) and grain-size determination per ASTM E112; Contractile Strain Ratio (CSR) when required shall be between 1.3 and 3.5 (AS 4076 method).
- Surface condition: OD chemical milling to remove at least 0.025 mm; ID chemical milling minimum 0.013 mm. Surface texture and ultrasonic inspection requirements are included.
- Testing: Includes ultrasonic inspection, flarability, bending, flattening, deformation-under-pressure, impulse pressure-fatigue (proof and pressure-impulse tests), and ultimate/burst testing as referenced.
Practical applications and users
- Primary users: aerospace OEMs, tubing manufacturers, suppliers of hydraulic tubing, aircraft maintenance organizations, quality and test laboratories, procurement/specification engineers.
- Applications: high-pressure aircraft hydraulic lines, aerospace fluid systems, pressure-critical tubing in landing gear, flight control actuators and other systems requiring lightweight, high-strength, corrosion-resistant tubing at 35 MPa.
Related standards (selected)
- ISO 8575 (aerospace hydraulic tubing dimensions)
- ISO 12573 (tubing tolerances - inch series)
- ISO 4287 (surface texture)
- ISO 6772, ISO 10583 (impulse testing and test methods)
- AS 4076, ASTM E112, EN 2003-010 (test methods and material analysis)
Keywords: ISO 18487-1, titanium tube, 35 MPa, aerospace tubing, pressure class J, seamless tubing, tensile properties, chemical composition, impulse pressure fatigue.